1. Field of the Invention
The present invention relates to a display device, and more particularly to a technique which is effectively applicable to a liquid crystal display device manufactured by a liquid-crystal dropping filling method.
2. Description of the Related Art
Conventionally, the TFT-type liquid crystal display device has been used as a display of portable electronic equipment such as a mobile phone terminal, an external display of a television receiver set or a personal computer (PC) and the like.
The TFT-type liquid crystal display device is a display device which includes a TFT-type liquid crystal display panel in which a liquid crystal material is filled between a pair of substrates. Here, the pair of substrates is adhered to each other using an annular sealing material (adhesive material), and the liquid crystal material is hermetically filled in a space defined by the pair of substrates and the sealing material.
Here, one of the above-mentioned pair of substrates is a substrate which is constituted by forming a plurality of scanning signal lines, a plurality of video signal lines, a plurality of TFT elements, a plurality of pixel electrodes, an alignment film and the like on a surface of an insulation substrate, and is generally referred to as a TFT substrate. Further, the other of the above-mentioned pair of substrates is a substrate which is constituted by forming, for example, a light blocking film (also referred to as a black matrix), color filters, a leveling film, a plurality of columnar members, an alignment film and the like on a surface of an insulation substrate, and is generally referred to as a counter substrate.
The plurality of columnar members formed on the counter substrate is basically provided for making a thickness of a liquid crystal material (cell gap) in respective pixels of the TFT-type liquid crystal display panel uniform and hence, conventionally, all columnar members are formed with the same height, that is, distances from a surface of the insulation substrate of the counter substrate to top portions of all columnar members have the same value.
On the other hand, with respect to the above-mentioned TFT-type liquid crystal display panel, for example, when a quantity of the liquid crystal material which is hermetically filled in the liquid crystal display panel is smaller than a predetermined quantity or when the liquid crystal material shrinks in a low-temperature environment, the TFT substrate and the counter substrate are deformed in the direction that the cell gap is decreased. Here, when the number of the columnar members is large, the deformation of the TFT substrate and the counter substrate is suppressed and hence, a negative pressure in the inside of the liquid crystal material is increased. Accordingly, in the conventional general TFT-type liquid crystal display panel, for example, bubbles may be generated in the liquid crystal material due to an impact which is generated when the TFT substrate and the counter substrate returns to an original state from a deformed state.
Accordingly, with respect to the TFT-type liquid crystal display panel, recently, for example, there has been proposed a method which can maintain a uniform cell gap by providing first columnar members and second columnar members which differ from each other in height on a counter substrate and, at the same time, can prevent the generation of bubbles in a liquid crystal material (see JP-A-2007-171716 (patent document 1), for example). Here, the second columnar members are formed lower than the first columnar members.